Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

315
FXUS63 KLOT 121825
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
125 PM CDT Tue May 12 2026

.KEY MESSAGES...

- Showers and perhaps a thunderstorm will move across the area
  in scattered fashion this afternoon.

- After a relatively cool Wednesday, temperatures will trend
  upward Thursday onward.

- The May 16 through 19 timeframe may feature several rounds of
  showers and storms in the general region.

&&

.DISCUSSION...
Issued at 125 PM CDT Tue May 12 2026

Rest of Today:

The center of a low pressure system is currently over
southwestern Lake Superior and is moving eastward toward the
Upper Peninsula of Michigan. A cold front extends southward
through western Wisconsin and across central Iowa away from the
center of the low pressure system. Meanwhile, a narrow band of
showers with embedded thunder associated with low-level
isentropic ascent continues to fester across far northern
Illinois and southern Wisconsin. Ahead of the region of showers,
the boundary layer is deep and well-mixed with air temperature
and dew point spreads pushing 20 to 25 degrees. Southwesterly
winds continue to increase with recent gusts of 30 to 35 mph
noted near the Mississippi River. While upper-level clouds will
spread over the rest of the area through the afternoon as the
band of showers tries to shift southeastward, the continued feed
of warm air from the southwest will help high temperature reach
the upper 70s to around 80 in the next few hours. The exception
will be near the Wisconsin state line where showers will hold
temperatures some 10 to 15 degrees lower.

As the band of showers shifts southeastward through the area
this afternoon, attention will turn northwest toward the cold
front for signs of convective development. Cooling mid-level
temperatures ahead of the parent trough shifting atop a plume of
surface dew points in the upper 40s to around 50 will allow for
around 250 J/kg of MUCAPE to materialize ahead of the front by
late afternoon. Provided the instability materializes, largely
uncapped mixed profiles should allow for at least isolated but
probably scattered high-based but low-topped convection.
Relatively shallow echo depths should tend to limit the
development of large hail. With that said, the deep dry profile
beneath the cloud bases will promote locally gusty winds with
the heartiest precipitation cores. In all, cannot rule out a
locally damaging gust this afternoon, mainly between 6 and 9 PM.
Clouds will clear quickly behind the cold front overnight.

Not to be forgotten, still am expecting at least patchy but
possibly areas of blowing dust to develop this afternoon along
and south of Interstate 80 where gusty southwesterly winds will
overlap with working agricultural fields. A plethora of personal
weather stations are showing gusts in excess of 35 mph south of
I-80 right now, so would expect the blowing dust threat to only
increase through the afternoon. The threat should end toward
sunset as boundary layer winds relax and rain arrives.

Tomorrow:

Deterministic guidance remains in agreement that a secondary
upper- level trough (currently racing into central Manitoba)
will move into the Great Lakes tomorrow morning. While the
timing will not be favorable to maximize diurnal heating,
steepening low-level lapse rates (by virtue of low-level cold
air advection to lower 850mb temperatures toward 0C) should
support the quick development of a stratocumulus deck by mid-
morning. Provided the depth of the cloud deck grows sufficiently
deep, cannot rule out instances of sprinkles across the area
from mid-morning to mid-afternoon. Highs will be noticeably
cooler than today and in the upper 50s along the lakeshore and
in northwestern Indiana to the mid 60s across central Illinois.

Clearing skies and the slackening wind field will set the stage
for temperatures to tumble tomorrow night. While the outgoing
forecast will feature overnight lows in the upper 30s to lower
40s, would not be surprised if actual lows verify even colder
and in the low to mid 30s. If such temperatures were to verify,
frost would be a definite threat.

Thursday onward:

Toward the end of the week and into the weekend, a well-
advertised change in the upper-level pattern will take place
with predominant cyclonic flow along the US/Canadian border
turns to quasi-zonal and eventually southwesterly. The net
effect will be a notable upward trend in temperatures as well as
a return of regular opportunities for springtime thunderstorms.
Note that the pattern will be supportive of severe
thunderstorms in general region, particularly Friday through
Monday.

Borchardt

&&

.AVIATION /18Z TAFS THROUGH 00Z THURSDAY/...
Issued at 109 PM CDT Tue May 12 2026

Key Messages:

- A band of showers will move through the area this afternoon
  with a few isolated lightning strikes possible (~20% chance).

- A secondary round of showers and possibly storms (~25-30%
  chance) may occur just ahead of a cold front this evening.

- Strong southwesterly winds are expected this afternoon with
  30+ kt gusts likely at times, though some uncertainty exists
  with the magnitude and frequency of these stronger gusts.

- A northeasterly wind shift behind a lake breeze may occur at
  ORD and MDW tomorrow afternoon.


At press time, a band of rain was entering northern Illinois
and gradually progressing east-southeastward. Dry sub-cloud air
was causing a lot of this precipitation to evaporate before
reaching the ground, but these showers were still making it to
the ground in spots. Would expect a similar theme to continue
through this afternoon as this rain band slides across the
terminals, and a brief period of MVFR visibility could not be
ruled out wherever the rain falls steadiest. Also noted a few
isolated lightning strikes near DBQ earlier, and additional
isolated lightning strikes may occur this afternoon. However,
the probability of one occurring near any particular TAF site
remains too low to warrant a formal VCTS or TSRA mention in the
TAFs through 00Z.

Additional showers may attempt to develop closer to an incoming
cold front this evening, possibly very near or directly over
the terminals. If this convection were to grow tall enough, then
it may also produce lightning. Confidence in this remains low,
but have maintained the inherited PROB30 groups for TSRA this
evening at the Chicago metro terminals.

Southwesterly winds are also expected to strengthen this
afternoon, though extensive mid- and upper-level cloud cover may
limit how high and how frequent the stronger (30+ kt) gusts
will be. Occasional gusts near 40 kts may nevertheless occur
near and during the showers/storms this afternoon and evening.
Winds will then shift to a northwesterly direction and subside
this evening behind the aforementioned cold front.

Late overnight into tomorrow morning, high-end MVFR ceilings may
be observed, but confidence in this is only low-medium and have
kept the TAFs VFR for now. A lake breeze is expected to develop
tomorrow afternoon and will likely cause a northeasterly wind
shift at ORD and MDW at some point. Confidence in the timing of
this wind shift remains low at this time.

Ogorek

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Blowing Dust Advisory until 7 PM CDT this evening for ILZ019-
     ILZ021-ILZ023-ILZ032-ILZ033-ILZ039-ILZ107.

IN...Blowing Dust Advisory until 7 PM CDT /8 PM EDT/ this evening
     for INZ010-INZ011-INZ019.

LM...Small Craft Advisory until 7 PM CDT Wednesday for the IL
     nearshore waters.

     Small Craft Advisory until 1 AM CDT Thursday for the IN
     nearshore waters.

&&

$$

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